The present invention relates generally to the communication of multimedia information, such as multimedia information formatted pursuant to the Real-Time Transport Protocol (RTP). More particularly, the present invention relates to apparatus, and an associated method, for converting real-time multimedia information, formatted in packet data form, such as that formatted pursuant to the RTP, into a form to facilitate transmission of the information on a radio channel. Operation of an embodiment of the present invention permits the communication of multimedia information by way of a cellular, or other radio communication system, with minimal time delay while also communicating the information in a spectrally-efficient manner.
Advancements in communication technologies have permitted the introduction of, and popularization of, new types of, and improvements in existing, communication systems. Increasingly large amounts of data are permitted to be communicated at increasing thruput rates through the use of such new, or improved, communication systems. As a result of such improvements, new types of communications, requiring high data thruput rates, are possible. Digital communication techniques, for instance, are increasingly utilized in communication systems to efficiently communicate digital data, and the use of such techniques has facilitated the increased data thruput rates.
Multimedia communications, for instance, are exemplary of new types of communications permitted as a result of the improvements in communications technologies. Multimedia communications refer, generally, to the communication of more than one type of data between a sending station and a receiving station. Typically, the communication of such more than one type of data appears, to a user, to be simultaneous. Multimedia communications include, for instance, voice-over-data applications. Audio signals overlaid upon video signals used to effectuate teleconferencing is an example of a multimedia communication application. Two-way white board communication is exemplary of another multimedia communication application.
The different types of data exhibit different communication requirements. For instance, voice data must be communicated in real-time. That is to say, voice data must be communicated without significant delay and must be communicated in a manner which permits its reconstruction at a receiving station in a manner which introduces minimal time distortion. Otherwise, the voice data shall appear to be noticeably distorted. Conversely, non-voice data is not as time-sensitive. However, more stringent accuracy requirements are associated with non-voice data.
Multimedia communications can be effectuated utilizing packet data communication techniques. With the popularization of the Internet and communication thereon, standardized, multimedia protocols have been set forth by which to communicate multimedia information in a form amenable to its transmission by way of the Internet. An example of multimedia protocol is H.323. H.323 is a widely used ITU standard which uses RTP.
According to the H.323 protocol, when multimedia data is to be transmitted by a sending station, logical channels upon which to transmit the data are assigned. The data channels are allocated responsive to requests made by the sending station. Separate logical channels are requested for separate types of data. For instance, a first logical channel is requested upon which to transmit voice data, and allocation of a second logical channel is requested for transmission of non-voice data. A subset of the H.323 protocol, referred to as the H.245 protocol, defines the manner in which the channels are requested. Packets of data are thereafter transmitted upon the logical channels. In conventional manner, the individual packets include header information, such as IP, UDP and RTP information, to identify to where the packet is to be directed and to provide a time stamp with the packet. The information of a packet of data, referred to as the payload, is appended to the header information.
The H.323 protocol was intended originally for wireline communications, such as between communication stations, connected by wireline connections including those of the Internet. But, advancements in communication technologies have also permitted the widespread usage of radio communication systems. A cellular communication system is exemplary of a wireless communication system which has achieved wide levels of popularity and usage. Telephonic communication by way of a cellular communication system mimics communication by way of a conventional wireline, telephonic system. However, because a radio-link is utilized in a cellular, or other radio, communication system, bandwidth considerations are generally more significant than when wireline networks are utilized for communications. That is to say, the radio-link upon which communication is communicated in a radio communication system is of a limited bandwidth capacity. And, by reducing the bandwidth requirements of information communicated thereon, the information capacity of the radio-link can be increased. So, efforts are made to minimize the bandwidth requirements of signals transmitted over the radio-link.
Information communicated pursuant to an H.323 protocol is predicated upon a packet-data configuration. The header information required of each packet of data is relatively bandwidth-consumptive. As a result, communication of multimedia information by way of a radio-link, such as that formed in the operation of a cellular communication system, is a relatively inefficient manner by which to communicate multimedia information. However, because the RTP-based protocol has become a defacto standard by which to format multimedia information, multimedia stations shall likely continue to be operable pursuant to such protocol irrespective of the bandwidth inefficiency of communication of packet data by way of the radio-link.
If a manner could be provided by which more efficiently to communicate multimedia information by way of a radio-link, while still utilizing the RTP-based protocol at the sending and receiving stations, improved multimedia communications by way of a radio communication system could result. It is in light of this background information related to multimedia communications that the significant improvements of the present invention have evolved.